August is often a mixed bag as far as the UK weather patterns are concerned. It has the capacity to be wet, windy and noticeably cooler in the evenings as it gets darker earlier, even though we are still in summer during that month. Yet in 2016, the month of August was hit with two instances of something called “The Spanish Plume”. It is an unusual weather effect, but far reaching in its consequences.
Defining A “Spanish Plume”
In simple terms, it is a warm and moist weather front that moves in from Iberia (the continental peninsula on which Spain and Portugal are located). Typically, it forms over the western Mediterranean and is pushed northwards through a chain of weather systems rather than staying in the south as expected.
Its effects are varied, but typically, we will immediately feel that the temperature is noticeably warmer than it was previously. The night temperature is balmy and the day temperature closer to 30C (86F). This air is also damp, leading to a greater risk of rain. In some areas, humidity will increase along with temperature, leading to greater risk of storms.
What Causes It?
Three conditions need to occur for a Spanish Plume event.
- Unusually warm air forms over the Iberian Peninsula (although it could start over the Sahara in North Africa) and, instead of staying where it is, warm air from the south pushes the front to the northeast
- Cooler air from the west pushes eastwards towards the British Isles and France
- Clear days and strong sunshine push up the temperatures
Together, these three basic effects work together and create a Spanish Plume when the heat from the south meets the colder air from the west. This can cause volatile weather patterns as we have seen in recent years, but it is not inevitable.
What Effects Does it Have?
The effects we experience from the Spanish Plume depend on how the three elements come together. There are positive and negative effects. August 2016 saw a mixture of effects across the country, but largely there were no issues except that heavy rain ruined a few barbecues in southern England. The Spanish Plume may sound like an attractive proposition as we head into September and towards autumn, but unlike an “Indian Summer”, there are potential negative consequences too.
Positive effects: Clear skies and warm sunshine is the most obvious effect. Late August can feel like early July when the conditions are just right. It’s the ideal time to head to the beaches and typically, the UK and northern France can have temperatures comparable with Spain and Southern France. Clouds may form, increasing humidity and temperature at the same time.
Negative effects: Storms are the most likely negative effect of The Spanish Plume. However, storms are not problematic in isolation, but summer storms resulting from The Spanish Plume can be much more intense and potentially dangerous. Tornadoes are likely, although nothing seen in France or the UK matches what is typically experienced in North America. Strong winds in the summer are often the result of The Spanish Plume, as are the increasing summer floods.
July 2014: A Week To Remember
We need only look back as far as July 2014 to see how bad the environment can get when such an event occurs. The UK was hit with several Spanish Plumes – one after the other in quick succession during the five-day period of the 17th to the 21st July. This was an unusual situation, especially considering that August 2016 saw two all month.
Intense thunderstorms and flash flooding hit many areas of the country; rain was heavy and prolonged. At Norwich Airport, 45.8mm of rain fell in just one hour – a month’s worth for the East Anglian city. During those five days, the UK experienced over 62,000 lightning strikes too. So although a Spanish Plume may sound attractive, its effects have the potential to devastate.